Energy or power may be transferred wirelessly using a variety of known techniques for, e.g., the purpose of doing work, such as for powering or charging electrical devices. For example, wireless power transfer systems (e.g., highly resonant wireless power transfer systems) may include high quality factor resonators that may be driven to generate oscillating electromagnetic fields and that may interact with oscillating magnetic fields to generate currents and/or voltages in electronic circuits. That is, energy may be transferred wirelessly using oscillating magnetic fields. For instance, wireless energy exchange between a source resonator (e.g., coupled to a power supply such as AC mains, battery, solar panels, etc.) and a remote resonator (e.g., integrated with electronic mobile devices, enclosures, sleeves, cases, covers, chargers, etc.) may exchange wireless energy, which as noted above, may be used to power or charge the associated electronic mobile device.
The wireless energy exchange between the source resonator and the remote (device) resonator may be optimized when the resonators are tuned to substantially the same frequency and when the losses in the system are minimal. As a non-limiting example, remote devices, such as a smart phone or other mobile electronic device, may be powered directly, using the wirelessly supplied power or energy, or the devices may be coupled to an energy storage unit such as a battery, a super-capacitor, an ultra-capacitor, or the like (or other kind of power drain), where the energy storage unit may be charged or re-charged wirelessly, and/or where the wireless power transfer mechanism may be supplementary to the main power source of the device. However, while known resonator designs may be optimized while at a distance, these resonators may be less optimal, e.g., in closer proximity. For instance, as a non-limiting example, the source resonator may detune the device resonator as each resonator moves closer in proximity to one another. Additionally, known current sensing techniques that may be used for wireless energy transfer may, e.g., have excessive loss and power dissipation for the high current and high frequencies used in some types of wireless energy transfer, may have frequency restrictions used in wireless energy transfer, may be susceptible to magnetic interference, may be expensive, and may add to the size of the overall devices.